1. Field of the Invention
The present invention relates to a display device and an electronic device using the display device.
2. Description of the Related Art
Transistors used for most flat panel displays typified by a liquid crystal display device and a light-emitting display device are formed using silicon semiconductors such as amorphous silicon, single crystal silicon, and polycrystalline silicon provided over glass substrates. Further, transistors using such silicon semiconductors are used in integrated circuits (ICs) and the like.
In recent years, attention has been drawn to a technique in which, instead of a silicon semiconductor, a metal oxide exhibiting semiconductor characteristics is used in transistors. Note that in this specification, a metal oxide exhibiting semiconductor characteristics is referred to as an oxide semiconductor.
For example, such a technique is disclosed in which a transistor is fabricated using zinc oxide or an In—Ga—Zn-based oxide as an oxide semiconductor and the transistor is used as a switching element or the like in a pixel of a display device (see Patent Documents 1 and 2).
A display device that includes a capacitor in which an oxide semiconductor film provided on the same surface as that on which an oxide semiconductor film of a transistor is provided and a pixel electrode electrically connected to the transistor are provided to be a predetermined distance apart from each other in order to increase the aperture ratio is disclosed (see Patent Document 3).
A method for manufacturing a thin film transistor in which including an oxide semiconductor film provided on the same surface as that on which an oxide semiconductor film serving as a pixel electrode is provided is disclosed (see Patent Document 4). In the manufacturing method, an oxide semiconductor film included in a pixel electrode is not patterned alone; an interlayer insulating film covers an oxide semiconductor film that is included in the thin film transistor, and plasma treatment is performed on an exposed portion of the oxide semiconductor film that is not covered by the interlayer insulating film to reduce the resistance of the oxide semiconductor film that is included in the pixel electrode.